title: Genetically induced mitotic exchange in the heterochromatin of Drosophila melanogaster.
abstract: Multiple copies of the 18S and 28S ribosomal RNA cistrons are present in both the X and Y chromosomes of Drosophila melanogaster. Data are presented here that identify a locus, Rex, that causes exchange-like events between duplicated ribosomal complexes at the ends of an attached-XY chromosome. Rex: (1) is close to or in the basal heterochromatin of the X chromosome; (2) is semidominant and (its effect) is temperature sensitive; (3) acts maternally; and (4) affects behavior of paternally derived attached-XY chromosomes shortly after fertilization. Though, at this point, the existence of Rex is known only from its effects on behavior of a particular compound chromosome, it presents intriguing possibilities for understanding regulation of chromosome behavior and organization of the ribosomal cistrons.
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D004331:Drosophila melanogaster / Q000235:genetics*; D005260:Female; D006570:Heterochromatin / Q000648:ultrastructure*; D008297:Male; D008938:Mitosis; D009030:Mosaicism; D011995:Recombination, Genetic; D013223:Statistics as Topic; D013696:Temperature; D014960:X Chromosome / Q000648:ultrastructure; D014998:Y Chromosome / Q000648:ultrastructure
chemical_list: D006570:Heterochromatin